Interference fit of cementless tibial implants and the initial mechanical environment: A micro-CT and DVC study.

During cementless total knee arthroplasty (TKA), an overlap between the resected tibia and the implant's geometry, termed interference fit, is introduced to facilitate primary stability and direct bone-implant contact. However, little is known about the actual interference achieved and the resulting mechanical response in the surrounding cancellous bone. The aim of this study was (1) to experimentally quantify the actual interference achieved for a commercially available cementless tibial implant and (2) to assess its effect on the post-impaction cancellous bone strain.

Quantifying the immediate post-implantation strain field of cadaveric tibiae implanted with cementless tibial trays: A time-elapsed micro-CT and digital volume correlation analysis during stair descent.

Primary stability, the mechanical fixation between implant and bone prior to osseointegration, is crucial for the long-term success of cementless tibial trays. However, little is known about the mechanical interplay between the implant and bone internally, as experimental studies quantifying internal strain are limited. This study employed digital volume correlation (DVC) to quantify the immediate post-implantation strain field of five cadaveric tibiae implanted with a commercially available cementless titanium tibial tray (Attune, DePuy Synthes).

Outcome following total knee replacement in patients with a previous patellectomy.

Although patellectomy is a rarely performed surgical procedure, patients may still progress to develop osteoarthritis of the tibiofemoral compartments leading to total knee replacement surgery. Due to the mechanical disadvantage of a previous patellectomy, it has previously been suggested that a prosthesis with more constraint should be used, however, there are conflicting reports in the literature. We aimed to assess the effects of stability following total knee replacement in patellectomised knee with revision as a primary endpoint.

Patellectomy for osteoarthritis: a new tension preserving surgical technique to reconstruct the extensor mechanism with retrospective review of long-term follow-up.

Background: The management of severe patellofemoral arthritis in young patients remains a significant problem. For many, patellofemoral replacement is not a desirable option. Current surgical techniques for patellectomy disrupt the extensor lever arm causing weakness.

Staged venous thromboemolic events prophylaxis with low-molecular-weight heparin followed by aspirin is safe and effective after arthroplasty.

Background: The rate of fatal pulmonary embolism (PE) following hip and knee arthroplasty has remained unchanged despite the use of low-molecular-weight heparin (LMWH) and oral antithrombotic agents. Concerns regarding bleeding and wound complications resulted in the introduction of a staged chemoprophylaxis protocol at our institution in 2002. We hypothesized that staged chemoprophylaxis using LMWH in hospital followed by aspirin after discharge was safe and effective for the prevention of venous thromboembolic events (VTE).

Revision of a fractured uncemented revision stem using a custom designed punch and retrograde through-knee approach.

We report a unique case of a fractured modular cobalt chromium connection taper Revitan (Zimmer, Warsaw, IN) revision prosthesis. Macroscopic examination revealed a fracture at the diaphyseal-metaphyseal junction of this modular component. This report highlights that fractures can still occur with modern modular prostheses.

Severe Heterotopic Ossification following Total Knee Replacement.

Although the incidence of minor heterotopic ossification is probably higher than what is usually expected, severe heterotopic ossification (HO) is an extremely rare event following total knee replacement surgery. We present the case of a 66-year-old woman who initially had achieved an excellent range of motion following bilateral uncemented rotating platform total knee replacement, before presenting with pain and loss of range of motion at 2 months after surgery. Severe HO was diagnosed on X-rays.

Early metallosis-related failure after total knee replacement: a report of 15 cases.

Metallosis is a rare cause of failure after total knee replacement and has only previously been reported when there has been abnormal metal-on-metal contact. We describe 14 patients (15 knees) whose total knee replacement required revision for a new type of early failure caused by extensive metallosis. A modification of a cementless rotating platform implant, which had previously had excellent long-term survival, had been used in each case.

Biomechanical testing of implant free wedge shaped bone block fixation for bone patellar tendon bone anterior cruciate ligament reconstruction in a bovine model.

Background: The use of an interference fit wedged bone plug to provide fixation in the tibial tunnel when using bone-patellar tendon-bone autograft for anterior cruciate ligament reconstruction offers many theoretic advantages including the potential to offer a more economical and biological alternative to screw fixation. This technique has not been subjected to biomechanical testing. We hypothesised that a wedged bone plug fixation technique provides equivalent tensile load to failure as titanium interference screw fixation.

Stem fracture of a collarless, polished, double-taper cemented femoral prosthesis: a case report.

We report a case of stem fracture of a collarless, polished, double-taper cemented stainless steel femoral prosthesis. Scanning electron microscopy showed fatigue striations, indicating failure by fatigue. This case study highlights that stem fracture can still occur with modern implants.

Lateral unicompartmental knee replacement: fixed or mobile bearing?

Between May 2001 and May 2003, 233 consecutive Preservation unicompartmental knee replacements (UKR) were performed. Of these, 30 were lateral UKRs (13%) performed in 12 men and 16 women (2 bilateral cases) with a mean age of 67 years (range 36-93 years). A metal-backed mobile bearing tibial component was used in 13 knees and an all-polyethylene fixed bearing tibial component in 17 knees.

Assessment of radionuclide arthrography in the evaluation of loosening of knee prostheses.

Background: Radionuclide arthrography (RNA) is an established technique in the evaluation of hip prostheses but there is scant literature on its role in knee prostheses and no data specifically related to unicompartmental knee prostheses. We reviewed our experience with radionuclide arthrography in total (TKRs) and unicompartmental (UKRs) knee arthroplasties.

Methods: A retrospective review of 66 consecutive RNA studies that either had direct surgical correlation or arthroscopic assessment in conjunction with at least 12 months of clinical and radiological follow-up.

Limb alignment in computer-assisted minimally-invasive unicompartmental knee replacement.

Twenty patients underwent simultaneous bilateral medial unicompartmental knee arthroplasty. Pre-operative hip-knee-ankle alignment and valgus stress radiographs were used to plan the desired post-operative alignment of the limb in accordance with established principles for unicompartmental arthroplasty. In each patient the planned alignment was the same for both knees.

Intraoperative arthrometry in anterior cruciate ligament reconstruction.

Arthrometry has an established role in the measurement of knee laxity in anterior cruciate ligament injury and following reconstruction. The role of routine intraoperative arthrometry in anterior cruciate ligament reconstruction is poorly defined, and this study was designed to test the hypothesis that intraoperative arthrometry provides an objective method of documenting successful knee stabilisation following anterior cruciate ligament reconstruction. A consecutive cohort of 100 patients with unilateral isolated anterior cruciate ligament disruption were prospectively evaluated using a Rolimeter arthrometer.

Cement retrieval in minimally invasive knee surgery: the 90 degrees ball probe.

Minimally invasive knee surgery has many potential advantages as well as disadvantages. One such disadvantage in both unicompartmental and total knee arthroplasty is the inability to visualize or retrieve extruded cement. We describe the use of a new instrument, a 90 degrees ball probe, which we have used in more than 300 minimally invasive unicompartmental knee arthroplasty cases.

Single photon emission computed tomography in planning unicompartmental knee arthroplasty. A prospective study examining the association between scan findings and intraoperative assessment of osteoarthritis.

The aim of this study was to determine the relationship between preoperative single photon emission computed tomography (SPECT) scan findings and intraoperative assessments of knee osteoarthritis (OA) in patients undergoing tibiofemoral unicompartmental knee arthroplasty (UKA). Fifty knees in 46 patients undergoing UKA were investigated preoperatively with a SPECT scan to confirm unicompartmental disease. There were 38 men and 12 women in the cohort with an average age of 63 years (range 44-78).

Haemoglobin levels following unicompartmental knee arthroplasty: influence of transfusion practice and surgical approach.

A retrospective review was undertaken of preoperative and day 3 postoperative haemoglobin (Hb) levels in all unicompartmental knee arthroplasty (UKA) procedures performed by a single surgeon. Sixty-six UKAs were performed using the same prosthesis through an open approach with patella eversion. This group was compared with 212 UKAs performed using a minimally invasive approach without patella eversion, with an implant and instrumentation specifically devised for this approach.

Injury to the infrapatellar branch of the saphenous nerve in anterior cruciate ligament reconstruction: comparison of horizontal versus vertical harvest site incisions.

Purpose: Damage to the infrapatellar branch of the saphenous nerve (IPBSN) has been described for knee arthrotomy and arthroscopy. The true incidence of damage to this structure during anterior cruciate ligament (ACL) reconstruction has not been reported. Furthermore, the traditional vertical incision for central patellar tendon harvesting runs perpendicular to the course of this nerve.

Polymerase chain reaction can detect bacterial DNA in aseptically loose total hip arthroplasties.

Identifying low-grade infection in failed total hip arthroplasties is an important but difficult task. This study investigated the ability of the polymerase chain reaction to identify low-grade infection during revision of total hip arthroplasties that failed from aseptic causes. One hundred thirteen specimens from 31 total hip arthroplasties revised for aseptic loosening were compared with 105 control specimens from 28 primary total hip arthroplasties.

Contamination of primary total hip replacements in standard and ultra-clean operating theaters detected by the polymerase chain reaction.

Background: Many organisms that are responsible for low-grade infection after total hip replacement (THR) are not recognized by routine culture.

Patients And Methods: We examined wound contamination during primary total hip replacement performed in standard and ultra-clean operating theaters. 20 THRs were performed in each type of theater.

Unicompartmental knee arthroplasty: an intermediate report of survivorship after the introduction of a new system with analysis of failures.

We describe the outcome of a series of 66 consecutive porous coated low contact stress (LCS) unicompartmental knee arthroplasty (UKA) cases performed in 52 patients for osteoarthritis (OA) by a single surgeon. Both survival, using the endpoint of revision for any cause, and knee function, using the Oxford knee score (OKS) as a validated outcome measure, were established in a retrospective review. At an average postoperative follow-up period of 5.

Cemented or uncemented hemiarthroplasty for displaced intracapsular femoral neck fractures.

The aim of this study was to establish whether or not to cement the hemiarthroplasty for displaced intracapsular femoral neck fractures in the elderly. Consecutive patients treated by hemiarthroplasty in adjacent hospitals were reviewed. The same monoblock prosthesis was used; in hospital A they were uncemented (121 patients), and in hospital B they were cemented (123 patients).

A survey of the treatment of displaced intracapsular femoral neck fractures in the UK.

A survey was undertaken to investigate the treatment of displaced intracapsular femoral neck fractures across the UK. The usual practice at 223 hospitals was recorded for two groups of patients, active and frail. Management of stereotyped fractures, in similar patients, varied between hospitals.